fix(rate UI): keep toolstrip menus inside constrained viewports

[d-sorgcodexagent]

Summary

• keep File, View, and Tools popovers inside a collision-safe 16 px viewport gutter
• preserve the desktop anchor and native details/summary keyboard/accessibility behavior
• reuse one fail-closed viewport-clamp contract across all three menus
• normally incorporate the exact repaired camera parent without rebasing, retargeting, rewriting, or force-pushing
• reconcile the canonical specification and all Rate handoffs in the same merge commit

Tracks #4300 under epic #4218. This draft does not close either issue.

Exact current topology

• head: 16a1167c31126238163297983862004afc5001d9
• first parent / prior qualified child: 5c8efcbe5fcd6f993ef947a85e39852d268780a6
• second parent / repaired camera PR feat(rate-of-closure): add camera tracking and snap views #4298: 104503aac9779b195d46d38e8ed32611ffc8dfd7
• preserved base: feat/4284-camera-snap-tracking
• immutable mobile implementation: ebd804ff24e7ce5ca58c7d1495c438ab1dcd83b5

Mobile-toolstrip production/test code did not conflict. Only four additive current-state handoff/spec files required reconciliation.

Current composed-tree verification

• 32 focused Python/PyQt camera and four-surface tests passed
• 8 focused React toolstrip/clamp tests passed
• 2 Chromium desktop/constrained-HiDPI menu cases passed
• TypeScript, zero-warning ESLint, and Vite production build passed (195 modules)
• pinned MyPy 1.13 passed 3 changed production files; Ruff/format passed 4 Python files
• four-surface authority, changed-Python policy, module-size, and whitespace gates passed
• exact repaired parent was independently qualified before propagation with 272 focused Python/PyQt tests, 670 React tests, 26 Rust tests, and pinned MyPy on 33 production files

Release boundary

Protected current-head CI, required review, native rendered qualification, installed UpstreamDrift conformance, parent integration, and dependency-ordered release remain open. This draft is not evidence that #4300, #4284, #4264, #4260, or #4218 is complete.

[dieterolson]

Superseded by #4466, which consolidates all 43 open src/rate_of_closure PRs into one
branch. Closing this one is measured, not assumed: verify_coverage.sh reports
safe=43 NOT-covered=0 against consolidated/rate-closure-remainder-2026-08-13, so this
PR's head is contained and nothing here is dropped.

Stacks were folded top-down (each child into its own parent, then the parent upward), so
non-tip work is included rather than skipped — including 8067ca79a (#4171, CAD export
artifact validation) and f9afa9d96 (#4309, strict ground result playback), each of which
lived in exactly one PR and is absent from its stack tip.

The consolidation also repairs defects the merge exposed, listed in #4466: two unguarded
datetime.UTC imports that break the Python 3.10 lane, a PyQt module registry that could no
longer construct the main window, the club-assembly binding and STL/sidecar controls that had
been dropped from the wired tree, and a filelock dependency that would have failed
tests (3.11) at collection.

Reopen this PR if you need its branch; the branch itself is untouched.